DD6 单晶合金涡轮叶片排气窗裂纹分析

针对DD6单晶合金涡轮叶片在试车一定时数后发生的排气窗裂纹故障,通过裂纹特征观察、断口形貌对比、金相组织检查、化学成分分析和微裂纹模拟试验等方法,进行裂纹性质及产生机理的研究。结果表明:叶片排气窗裂纹性质为疲劳裂纹,起源于间隔墙转接部位再结晶晶界处的微裂纹;试车时振动应力的作用使微裂纹扩展;间隔墙部位的再结晶晶粒在试车前已经存在,与过大的铸造残余应力有关,再结晶检验时腐蚀液侵蚀再结晶晶界形成微裂纹;在叶片铸造时,型芯强度对间隔墙再结晶有明显影响,型芯的强度越高,产生再结晶的几率越大。

Crack Analysis of Exhaust Window of DD6 Single Crystal Alloy Turbine Blade

In view of the crack failure of exhaust window of DD6 single crystal alloy turbine blade after a certain number of hours of the test run,the crack property and mechanism were studied by means of crack characteristics observation,fracture morphology comparison,metallographic examination,chemical composition analysis and microcrack simulation test.The results show that the crack property of the blade exhaust window is fatigue crack,which originates from the recrystallization boundary of the partition wall.The action of vibration stress during test run makes the crack propagation.Recrystallization grain of the partition wall part has existed before the test run,which is related to the excessive casting residual stress,and the corrosion liquid attack the recrystallization grain boundary to form the microcrack at the time of the recrystallization test.In blade casting,the strength of the core has an obvious effect on the crystallization of the partition wall.The higher the strength of the core,the greater the probability of recrystallization.